The studies proposed are directed to investigate experimentally the interactions between "Light" (primarily ultraviolet radiation), chemical agents of occupational importance and biologic systems (primarily the skin). The major objectives are to investigate and identify factors predisposing to occupational, "Light" induced skin damage; to evaluate the influence of selected classes of chemical agents on skin phototoxicity and photocarcinogenesis; and to develop protocols and experimental animal systems for future bioassay tests. Approaches to be utilized consist of photochemical studies of biological active chemicals, augmentation and/or promotion of photocarcinogenesis in mice, studies of DNA repair of human lymphocytes and measurement of UVR dose to man with newly developed personal dosimeters.